1. Field of the Invention
The present invention relates to messages sent and/or received by mobile radio terminals such as mobile telephones.
2. Description of the Prior Art
The exchange of Short Message Service (SMS) short messages has grown considerably in recent times. Conventionally, an SMS comprises a transport protocol data unit (TPDU), shown diagrammatically in FIG. 1.
The TPDU includes a transport protocol (TP) header associated with the transport protocol used and TP user data. The TP header contains transmission information such as the destination address (TP-DA), which can be a telephone number or an electronic address, for example, the identification of the transport protocol used, which can be a file, hypertext, radio or other transport protocol, the length of the data of the message (TP-UDL), and other information relating to the routing of the message, such as the time, the presence of a header in the data, etc. Some of this information is mandatory and some is optional. The SMS message data (TP User Data) includes a user data header (TP-UDH) followed by the message itself, referred to as the user data (TP-UD).
As initially developed, short messages included only text, without any multimedia data such as music or pictures, for example, and did not contain a great deal of information. Accordingly, a single data unit (TPDU) was able to transport the information to be transmitted. However, the development of Enhanced Message Service (EMS) short messages has recently expanded and has led to the issuing of a recommendation on this subject in the form of the SMS standard 3GPP TS 23.040. An enhanced message can contain much more information, which generally makes it essential to concatenate data units (TPDU) to transmit EMS via a mobile radio network.
In an EMS message, the data header (TP-UDH) includes an indication of the length of the header (UDHL) and at least one information element (IEI) followed by the data of the message (User Data). The information elements IE can contain multimedia data to be associated with the EMS enhanced message. Each information element IE contains an identification field (IEI) followed by a field (IEDL) indicating the length of the element followed by the data of the element (IED). Accordingly, the text (User Data) of the EMS message contains calls to the various IE defined in the header to be integrated into the data of the message transmitted.
A new type of message has recently been developed, known as Multimedia Messaging Service (MMS) messages. MMS messages, which are shown diagrammatically in FIG. 2, have a transmission protocol and a structure completely different from those of SMS and EMS messages, and are standardized in 3GPP Recommendation TS 23.140. MMS messages have a structure defined by the IETF (in RFC 2045) consisting in a Multipurpose Internet Mail Extensions (MIME) file format, with a header and a message body that can contain pictures, music, text and a presentation of graphical elements on the screen as well as temporal synchronization of some elements. An MMS message can include much denser multimedia data than an EMS message and provide richer multimedia presentations, of the type available on computers, for example. MMS messages are generally transmitted in accordance with the wireless application protocol (WAP).
The exchange of MMS messages presupposes the presence in the mobile radio network of a particular server dedicated to MMS messages which is separate from the server dedicated to SMS and EMS messages. Furthermore, the sending and/or receiving of MMS messages by a terminal is conditional on the installation of particular application software necessitating the allocation of high memory and processing capacities. Low-cost terminals and terminals of an older generation cannot support an application of this kind, although they can exchange SMS and EMS messages.
The use of MMS messages is therefore restricted to terminals which are capable of supporting this kind of application, which significantly reduces the interest in exchanging such messages and is retarding the growth of this new type of message. Moreover, some terminals incorporate the MMS application but reject the EMS application, although they retain the possibility of exchanging SMS.
Furthermore, different versions of EMS messages have already been developed, later ones generally being compatible with earlier ones. Nevertheless, sending an EMS message from a terminal integrating a new version (for example release 5) to a terminal having only the old version (for example release 4) can lead to defective display of the content of the message.
An objective of the invention is therefore to address the problem of interworking between the MMS message system and the SMS/EMS message system, as well as between different versions of the EMS message system, by proposing to adapt the content of messages transmitted to suit the reception possibilities of the terminal to which the message is addressed.